Process for making chlorotrifluoroethylene from 1,1,2-trichlorotrifluoroethane

ABSTRACT

Disclosed is a process for the making chlorotrifluoroethylene. The process comprises the step of reacting 1,1,2-trichlorotrifluoroethane with a reducing metal in the presence of a polar aprotic solvent under conditions sufficient to form chlorotrifluoroethylene.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of application Ser. No.12/537,805 filed Aug. 7, 2009, now U.S. Pat. No. 7,723,552. The '552patent claims domestic priority from U.S. Provisional Application No.61/087,482, filed Aug. 8, 2008. The disclosures of these applicationsare hereby incorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to a process for the makingchlorotrifluoro-ethylene (CFO-1113) from 1,1,2-trichlorotrifluoroethane(CFC-113).

BACKGROUND OF THE INVENTION

Chlorotrifluoroethylene (CFO-1113) is currently manufacturedcommercially by dechlorinating 1,1,2-trichlorotrifluoroethane (CFC-113)via reaction with zinc in the presence of methanol as a solvent. A majordrawback with this process is the formation of1,2-dichloro-1,1,2-trifluoroethane (HCFC-123a) as a major byproduct,which greatly reduces the yield of CFO-1113 and is costly to dispose of.

It would be desirable to have an improved process for making CFO-1113from CFC-113.

SUMMARY OF THE INVENTION

According to the present invention there is provided a process for themaking chlorotrifluoroethylene. In one embodiment, the method has thestep of reacting 1,1,2-trichlorotrifluoroethane (CFC-113) with areducing metal in the presence of one or more polar aprotic solventsunder conditions sufficient to form chlorotrifluoroethylene (CFO-1113).

In certain embodiments, the one or more polar aprotic solvents isselected from the group consisting of aldehydes, ketones, dimethylsulfoxide, dimethyl formamide, and combinations thereof. In certainembodiments, the aldehydes have the formula R—CHO, wherein R is an alkylgroup having from 1 to 4 carbon atoms. In certain embodiments, theketones have the formula R—CO—R′, wherein R and R′ are alkyl groups,each independently having from 1 to 4 carbon atoms.

In certain embodiments, the one or more polar aprotic solvents isselected from the group consisting of ethyl ether, ethyl acetate,acetone, methyl ethyl ketone, and combinations thereof.

In certain embodiments, the polar aprotic solvent comprises ethyl ether.In certain embodiments, the polar aprotic solvent comprises ethylacetate. In other embodiments, the polar aprotic solvent comprisesacetone. In other embodiments, the polar aprotic solvent comprisesmethyl ethyl ketone.

In certain embodiments, the reducing metal is selected from the groupconsisting of zinc, magnesium, aluminum, and tin. In certainembodiments, the reducing metal comprises zinc. In certain embodiments,the reducing metal comprises magnesium. In certain embodiments, thereducing metal comprises aluminum. In certain embodiments, the reducingmetal comprises tin.

In certain embodiments, the reaction is carried out at a temperature offrom about 50° C. to about 100° C. In certain embodiments, the reactionis carried out at a temperature of from about 60° C. to about 90° C. Incertain embodiments, the reaction is carried out at a temperature offrom about 60° C. to about 85° C.

In certain embodiments, the reaction is carried out in batch mode. Incertain embodiments, the reaction is carried out in continuous mode.

It should be appreciated by those persons having ordinary skill in theart(s) to which the present invention relates that any of the featuresdescribed herein in respect of any particular aspect and/or embodimentof the present invention can be combined with one or more of any of theother features of any other aspects and/or embodiments of the presentinvention described herein, with modifications as appropriate to ensurecompatibility of the combinations. Such combinations are considered tobe part of the present invention contemplated by this disclosure.

DETAILED DESCRIPTION OF THE INVENTION

The process of the present invention has the following reactionsequence:CFCl₂—CF₂Cl+M→CF₂═CFCl+MCl_(x)(CFC-113) (CFO-1113+metal chloride)wherein M is a reducing metal and wherein the dechlorination reaction iscarried out in the presence of a polar aprotic solvent. When M is zinc,the reaction sequence is the following:CFCl₂—CF₂Cl+Zn→CF₂═CFCl+ZnCl₂(CFC-113) (CFO-1113+zinc chloride)

Polar aprotic solvents are solvents that have similar dissolving powerto protic solvents, but without the presence of an acidic hydrogen.Useful polar aprotic solvents include, but are not limited to, aldehydes(R—CHO), ketones (R—CO—R′), dimethyl sulfoxide (DMSO) (CH₃—SO—CH₃),dimethyl formamide (DMF) (H—CO—N(CH₃)₂), and combinations thereofwherein R and R′ are alkyl groups having 1 to about 4 carbon atoms.Additional examples of useful polar aprotic solvents include ethylether, ethyl acetate, acetone, and methyl ethyl ketone. Aprotic solventshave the advantage of producing lower amounts of byproducts. Moreparticularly, polar aprotic solvents have the advantage of producinglower amounts or none of the byproduct HCFC-123a.

Although not wishing to be bound by any particular theory, it isconjectured that protic solvents (e.g., methanol) cause the formation ofHCFC-123a by losing an acidic hydrogen to a reaction intermediate. Useof polar aprotic solvents will reduce or eliminate the formation ofhydrogen-containing byproducts.

Useful polar aprotic solvents are those capable of dissolving thereactant and the reaction products, i.e., CFC-113, CFO-1113 and MCl_(x),i.e., a chloride of the reducing metal. A polar aprotic solvent ispreferably used in an amount sufficient to substantially dissolve thereactant and the reaction products.

The solvent system may be made up substantially or entirely of a polaraprotic solvent(s) or combinations of a polar aprotic solvent(s) and aprotic solvent(s). In the instance of combinations, the amount of proticco-solvent can range from about 1 wt. % to about 80 wt. % and morepreferably about 5 wt. % to about 40 wt. % based on the total weight ofthe polar aprotic solvent(s) and the protic co-solvent(s).

Protic co-solvents useful in combination with the aprotic solventsinclude methanol, ethanol, propanol, isopropanol, and water.

Useful examples of suitable reducing metals include zinc, magnesium,aluminum, and tin. A preferred reducing metal is zinc.

The dechlorination reaction is carried out under conditions sufficientto form chlorotrifluoroethylene. The reaction is preferably carried outat a temperature of about 50° C. to about 100° C., more preferably about60° C. to about 90° C., and most preferably about 60° C. to about 85° C.The reaction can be carried under vacuum, atmospheric, orsuperatmospheric pressure conditions. The reaction vessel is preferablyan agitated pressure vessel. The process can be either batch orcontinuous.

The following are examples of the present invention, and are not to beconstrued as limiting.

EXAMPLES

Examples of the process of the invention and a comparative example weretested for conversion.

Comparative Example

In a plant operation test, only a protic solvent, MeOH, was used.Starting materials of 1.08 liters of methanol and 0.32 kilogram of zincper kilogram of CFC-113 were charged into a batch reactor equipped withagitation. The reaction was carried out at about 73° C. The conversionof CFC-113 and selectivity to CFO-1113 were 92.4% and 94.1%,respectively.

Example 1

This is an example that demonstrates using only an aprotic solvent.Here, 65 grams of zinc powder was charged into a one-liter agitatedpressure vessel. The vessel was then sealed, pressure checked, andevacuated. Approximately 175-250 milliliters of acetone were chargedinto the reactor on top of the zinc followed by an addition of 200 gramsof CFC-113. The vessel was heated to a temperature necessary to run thereaction, approximately 60° C. to 85° C. with agitation. The reactionwas run for 220 minutes after the temperature was stabilized at thedesired setting. During the reaction, the pressure rose to 150 psig.After the run was completed, the volatile reaction products weretransferred to a chilled and evacuated product collection cylinder byventing the pressure from the reactor down to atmospheric. The collectedmaterial was analyzed using Gas Chromatography (GC) which revealed thatconversion of CFC-113 was 88.6%, while selectivity to CFO-1113 was99.8%.

Example 2

The process of Example 2 was run substantially as described in Example 1except that a mixture of acetone and methanol (80:20) was used as thesolvent instead of acetone alone. Conversion of CFC-113 and selectivityto CFO-1113 were 99.4% and 99.6%, respectively. The presence of methanolhad the effect of increasing conversion and the presence of the polaraprotic solvent, acetone, improved selectivity to CFO-1113.

It should be understood that the foregoing description is onlyillustrative of the present invention. Various alternatives andmodifications can be devised by those skilled in the art withoutdeparting from the invention. Accordingly, the present invention isintended to embrace all such alternatives, modifications and variancesthat fall within the scope of the appended claims.

1. A process for the making chlorotrifluoroethylene, consisting ofreacting 1,1,2-trichlorotrifluoroethane with reagents consistingessentially of a reducing metal in the presence of one or more polaraprotic solvents under conditions sufficient to formchlorotrifluoroethylene.
 2. The process of claim 1, wherein the one ormore polar aprotic solvents is selected from the group consisting ofaldehydes, ketones, dimethyl sulfoxide, dimethyl formamide, andcombinations thereof.
 3. The process of claim 2, wherein the aldehydeshave the formula R—CHO, wherein R is an alkyl group having from 1 to 4carbon atoms.
 4. The process of claim 2, wherein the ketones have theformula R—CO—R′, wherein R and R′ are alkyl groups each independentlyhaving from 1 to 4 carbon atoms.
 5. The process of claim 1, wherein theone or more polar aprotic solvents is selected from the group consistingof ethyl ether, ethyl acetate, acetone, methyl ethyl ketone, andcombinations thereof.
 6. The process of claim 1, wherein the polaraprotic solvent comprises ethyl ether.
 7. The process of claim 1,wherein the polar aprotic solvent comprises ethyl acetate.
 8. Theprocess of claim 1, wherein the polar aprotic solvent comprises acetone.9. The process of claim 1, wherein the polar aprotic solvent comprisesmethyl ethyl ketone.
 10. The process of claim 1, wherein the reducingmetal is selected from the group consisting of zinc, magnesium,aluminum, and tin.
 11. The process of claim 1, wherein the reducingmetal comprises zinc.
 12. The process of claim 1, wherein the reducingmetal comprises magnesium.
 13. The process of claim 1, wherein thereducing metal comprises aluminum.
 14. The process of claim 1, whereinthe reducing metal comprises tin.
 15. The process of claim 1, whereinthe reaction is carried out at a temperature of from about 50° C. toabout 100° C.
 16. The process of claim 1, wherein the reaction iscarried out at a temperature of from about 60° C. to about 90° C. 17.The process of claim 1, wherein the reaction is carried out at atemperature of from about 60° C. to about 85° C.
 18. The process ofclaim 1, wherein the reaction is carried out in batch mode.
 19. Theprocess of claim 1, wherein the reaction is carried out in continuousmode.